RIO DE JANEIRO, June 21 (Reuters) - Sanitation company Aegea and Equatorial Energia are among the investors interested in the share offering that will privatize Sao Paulo state water utility company Sabesp, according to three sources with knowledge of the matter on Friday.

Brazilian businessman Nelson Tanure has also considered the possibility of bidding, according to the sources, although he is not expected to compete for a stake in the firm.

Aegea and representatives of Tanure did not comment. Power firm Equatorial said it will not comment over specific possibilities of deal or acquisitions.

On Thursday, the Sao Paulo government gave its final approval on the privatization, which will be carried out through an unusual two-part share offer.

According to the sources, the offer prospectus will be released on Friday and the roadshow to publicize the operation will begin next week.

Sabesp is looking for a reference shareholder who would hold a 15% stake. The State of Sao Paulo, which owns 50.3% of the company, intends to keep a minority stake after the offer.

(Reporting by Rodrigo Viga Gaier; Writing by Peter Frontini; Editing by Louise Heavens)